Color photography



Patented Nov. 14, 1944 2,302,599 COLOR rno'rooanrnr Paul W. Vlttum, Rochester, N. Y.. assignor to Eastman Kodak Company, Rochester, N. Y., a. corporation of New Jersey No Drawing. Application September 10, 1942.

Serial No. 457,869

t 2 Claims.

This invention relates to a multi-layer material for color photography.

Multi-layer materials in which a coupler compound capable of coupling with the oxidation product of an aromatic amino developing agent is dissolved in a water-insoluble solvent and the v solution dispersed in the emulsion layer have been described in Mannes and Godowskv U Patents 2,304,939 and 2,304,940 granted December 15, 1942,. and in J elley and Vittum U. S. Patent 2,322,027, granted June 15, 1943. It has been established that these processes which yield final dye images consisting of highly dispersed dye coupler itself may be unstable under severe condltions and decompose to yield dark colored products which reduce the value of the picture.

This diiii-culty encountered by the presence of the residual coupler is most noticeable in the case of couplers which produce yellow dyes upon development, particularly yellow couplers of the acylacetanilide type. Such couplers absorb ultra-violet llghtusually in the region between 3% and 350 millimicrons. This absorbed light effects a photochemical reaction whereby the coupler becomes colored or destroys the dye in contact with it. In a finished layer containing dye and residual coupler,, this light-absorption property of the residual coupler exerts a deleterious effect. The yellow dyes themselves do not absorb in the region of 300-350 millimicrons, and therefore are not affected by ultraviolet light in the same way as the-residual couplers. In the customary arrangement of multi-layer materials, the coupler producing the yellow dyeis located in the top emulsion layer. It is, therefore, desirable to eliminate the residual coupler from the top emulsion layer of a multilayer material containing couplers.

It is an object of. the present invention to provide a. method for improving the quality of color pictures in multi-layer materials. A further object is to provide a method for obtaining'the, inherent advantage of color pictures produced tram dyes in dispersed solution in the gelatin while overcoming the disadvantages of the presence of residual coupler in the top layer of the material. A still further object is to provide a method for processing a multi-layer material having dispersed couplers in the lower layers and no coupler in the top emulsion layer. Other objects will appear from the following description of my invention.

These objects are accomplished by incorporating in the lower emulsion layers of a multi-layer material dispersed particles of coupler and solvent for the coupler and processing the film so that a yellow dye image is produced in the top layer which contains no coupler prior to processing of the material.

According to my process the normal dye images are produced in the lower layers of a multi-layer material by a single development step and the dye image is produced in the top emulsion layer either at the same time or at an earlier or later time by a separate development step. This method permits the use of a material which contains no coupler in the top layer, and, therefore, no residual coupler is present in the layer. In the case of couplers of the acyl acetanilide type, customarily employed for the formation of a yellow dye image, the presence of the residual coupler is especially objectionable. It has been found that while the yellow dye is relatively quite fast to light, the presence of small amounts of unused coupler renders the dye image in this layer much less stable to light.

Various procedures may be used to obtain the combination of dye images necessary to produce a natural color picture according to my invention. Examples of such procedures are as follows:

A. In'the case of a multi-layer material having the usual emulsion layers sensitive respectively to the red, green and blue regions of the spectrum, the red-sensitive layer is customarily, nearest the support, the green-sensitive layer in the middle and the blue-sensitive layer outermost. A yellow filter layer is customarily placed between the top and middle emulsion layers or the filter material maybe in the top layer itself. According to my invention the red-sensitlve and green-sensitive layers would contain dispersed particles of coupler and solvent therefor such as described in Mannes and Godowsky U. S. Patent. 2,304,940 or Jelley and Vittum U. S.

Patent 2,322,027. After exposure of such a material, the top emulsion layer is developed first bya developing solution containing the desired controlled by proper timing or by the use of loading agents in the solution. Asuitable de-' veloping solution is as follows: A. 2-amino-5-diethylamino toluene HCl Isoproply alcohol do-- 100 For use, B is addedto A.

After this development step, development of the lower layers of the film is carried out in the customary developing solution containing no cou-' pier. This developer may have the following composition:

2- amino-5-diethylamino toluene HCl grams 2 Sodium sulflte do 2 Sodium carbonate do 20 Potassium bromide dn 3 Water to I litnr 1 The silver images and residual silver halide are then removed by treatment with ferricyanide and hypo, and washing completes the process.

B. The material described in A is developed in the normal color developer containing no coupler such as that referred to in A to yield silver and dye images in'the lower emulsion layers and to produce a silver image only in the top layer. The unused silver halide in the material is then fixed out and the silver in the top layer or in all of the layers is rehalogenized in a well known manner. The material is then treated with a color developing solution containing the desired coupler which forms the dye image in the top layer alone. This solution may havethe following composition:

A. 2-amino-5-diethylamino toluene HCl BisaddedtoA. Silver removal and washing complete the C. For the production of the dye image in the top emulsion layer a coupler may be used which is so constituted that its diffusion into the film is I slow and controllable. 'A yellow coupler of this type is p-benzeneazoacetoacetanilide. In this case, the slowly diffusing coupler can be added directly to the color developer and the upper dye image produced from the coupler in the solution, and the lower dye images produced from the coupiers in the layers in a single developning operation. The developing solution specified in B withthe substitution of p-benzeneazoacetoacetanilide M n- NObbNi compared with the rates of reaction of the coupiers present in the lower emulsion layers such as the red-sensitive and green-sensitive layers constituted as described in A but having in the bluesensitive top layer a dispersion of a solvent; for the dye. In order to produce an emulsion layer having the maximum transparency, it is desirable that this solvent have approximately the same refractive index as the gelatin and it should also be relatively insoluble in water, have a high solvent action for the dye to be produced in the layer and be inert to the sensitive emulsion and to the dyes and processing solutions. Solvents of this type are described in Jelley and Vittum Patent 2,322,027, referred to above. The following com pounds are suitable as dye solvents:

N,n-amylphthalimide N,n-amylsulcinimide n-Butylphthalate Methyl phthalate Veratrole Methyl-p-toluene sulfonate Ethylphthalylethylglycollate 'lri-o-cresylphosphate These solvents produce liduid dispersions of the dye in the emulsion layer. Mixtures of two or more solvents may be used in some cases or it may be desirable to add to the solvent another ingredient such as a cellulose derivative or natural or synthetic resin to reduce the fluidity of the solvent, to change its refractive index or for some other purpose.

The top emulsion layer containing the dispersed solvent for the dye may be produced as follows:

A mixture of 20 grams of n-butylphthalate and 20 cc. of ethylacetate is added to 200 cc. of water containing 1 gram of sodium lauryl sulfate. The

whole mixture is thoroughly emulsified, for example, by passing it through a colloid mill and the resultant fine dispersion added to 1000 cc. of the melted gelatino-silver halide emulsion. This is then coated as the top layer of the film and dried in the usual manner. v This material may beprocessed by any of the methods described above, the dye produced being dissolved in th dispersed particles of the solvent.

Other methods of operation will suggest them selves for the production of negative images in the material and reversal images may be obtained by adaptation of these or other methods.

Any suitable primary aromatic amino developing agent may be used in my process such as diethyl p phenylenediamine hydrochloride,

for the coupler used in that example is suitable.

Alternatively, the top layer can be developed in a developing solution containing the slowly diffusing coupler and the bottom layers-developed subsequently in a developing solution containing no coupler.

D. For the production of the dye image in the top emulsion layer of the material described in A,

a coupler can be used which has a relatively low rate of reaction with theoxidized developer as monomethyl pphenylenediamine hydrochloride, 2-amino-5-diethylaminotoluene hydrochloride, and dimethyl-p-phenylenediamine sulfate. These compounds have an unsubstituted amino group which enables the oxidation product of the developer to couple with the color-forming compounds.

My process maybe used for the production of colored photographic images in layers of gelatin or other carrier such as collodion or an organic acid ester of cellulose. The carrier for the sensitive material may besupported by glass or a flexible film such as cellulose nitrate or cellulose acctate. The emulsion layers may also be coated which difluses only through the top layer in the on an opaque support such as paper or pigmented cellulose ester.

It will be understood that the examples included herein are illustrative only and that my invention is to be taken as limited only by the scope of the appended claims.

I claim:

l. The method of producing a natural-color image in a multi-layer photographic material, at least one lower layer of which is a silver halide layer containing dispersed particles of a solution of color-former and a water-permeable, waterinsoluble solvent for the color-former, and the top layer of which is a silver halide layer free or color-forming material, which comprises exposing both layers or said material and developing them in a color-tor developer containing a coupler time required to develop all of the layers.

2. The method of producing a natural-color image in a multi-layer photographic material, at least one lower layer of which is a silver halide layer containing dispersed particles of a solution of color-former and a water-permeable, waterinsoluble solvent for the color-former, and the top layer of which is a blue-sensitive silver halide layer free of color-forming material, which comprises exposingthe sensitive layers of said material and developing them in a color-forming developer containing a coupler which diduses only through the top layer and which produces a yellow image therein in the time required to develop all of the layers.

. PAUL W. VITTUM. 

